Structural Characterization of an Ethylene-Tetrafluoroethylene Alternating Copolymer by Polarized Raman Scattering

The anisotropic scattering properties of a uniaxially oriented filament of an ethylene-tetra-fluoroethylene (E-TFE) alternating copolymer have been investigated in order to determine the molecular conformation in ordered crystalline regions. Both a trans-planar and a 3/2-helical structure have been shown to be energetically possible in an isolated molecule and in this study the group theoretical analyses for these structures are presented. Comparison of these results with polarized Raman measurements indicates that the copolymer backbone crystallizes in predominantly a planar-zigzag structure. Observation of the low-frequency Raman-active longitudinal acoustical mode (LAM) and the correlation of its frequency position with the crystalline stem length obtained from SAXS and crystallinity measurements strongly support the trans-planar structure. © 1983, American Chemical Society. All rights reserved.